Poly bi wife speaking here
My writing skills are not as eloquent or cultured as many are here, so I will do my best.
I can't speak for my sweetheart on this, but I hope that she has benefits.
The obvious would be that she is also bi, and having a male and female available for sex is great.
I hope that she feels equal to me and our hubby. I would never want to bring someone into my life and make them feel second class. I could go into the details of my upbringing in a patriarchal Mormon home, but that is another discussion. I struggled to break away from the damage done to my self-worth from being taught that I was second class and that is just how God wants it. I never ever ever want to be the one who creates that situation for another human being.
Thank the gods for a loving husband whose love helped me find myself as a whole, important, valued individual.
If she did come to us with a low self-esteem, hopefully we could help change that through being loving and considerately supporting her needs, desires and dreams. I would definitely want her to grow and flourish. I doubt she is too insecure. She is a former Marine. She has a master's degree. She is much more accomplished (and younger) than I am (which makes ME feel insecure, sometimes

).
I would be a liar if I didn't point that we are still working on the primary-secondary thing. For instance, when we get into hubby's car to go somewhere, she looks at me to see if I want the seat next to hubby. This is actually progress, however, because initially I couldn't get her to sit next to him, anywhere, unless there was room for me directly next to him on the other side. I think she doesn't want to make me feel less important.
Hubby and I have a more matured relationship, which may make it seem more primary, but the NRE that she brings often outshines it. She has expressed to me that sometimes she feels like hubby and I have each other, and she is a third party, on the side. Wow, how did that happen? I try so hard to avoid it,, and will continue working on it. Perhaps moving in together would help, but she is not ready to give up her apartment. We sure miss her when she is not with us. She has changed our couple relationship, we will never be the same again, with or without her.
She is getting two people who have had to learn to negotiate in order to keep our relationship a loving and fulfilling experience. We carry that into the changing dynamic of our new threesome.
Comprises? Some are easier, because we can take a 2 out of 3 vote in many situations. Hubby might not find this a fair solution, as it is 2 women against 1 man.
I also want to point out that we are talking about poly relationships. Isn't it possible to have a primary and a secondary in any poly relationship? Some mono wives often express feelings of being secondary to a mother-in-law, or her husband's buddies.
Someone might think that a wife who stays with a husband that wants another woman must have some self-esteem issue, Right? Maybe I am the one with the low self-esteem.
I came to this forum searching for answers. I learned that love is not monogamy-dimensional. Being here at this forum helped me to open my mind. When I opened my mind, my heart got bigger. Isn't that what makes poly so awesome?
I would love input. This thread has given me a lot to think about since yesterday.